The present invention pertains to an exothermic resistor type air flow detector suitable in particular for fuel control of automobile engines.
Air flow detectors are used in various areas, including process control at chemical plants and air conditioning systems for buildings. In automobiles, in particular, there is a need to accurately control the mixture of the fuel supply, for environmental protection purposes, as well as for resource conservation. For this reason, there is a growing need for an air flow detector that detects engine air intake. Such detectors are expected to become commonplace in the future.
One known air flow detector is the so-called heating resistor type, which detects the air flow from the heat value which it takes away from a heating resistor. However, mechanical strength and resistance against intrusions such as dust (maintaining precision of detection) are important attributes in an air flow detector of this type. For this reason, a detector that uses a laminar substrate with a filmy exothermic resistor formed on its surface has been proposed in the past, an example of which can be seen in Laid Open Japanese Patent Application No. 63-134919.
Such conventional technology requires a large amount of electricity for heating the exothermic resistor. However, heretofore no consideration has been given to the substantial heat generated in the control circuit that handles this heating electricity, and it has therefore been necessary to provide a large radiation structure in the control circuit, which has made it difficult to achieve a compact air flow detector design.